How Many Species are on Earth?

For several years scientists have tried to estimate the number of species living on Earth. This is not an easy question to answer and multiple approaches have been developed to calculate how large Earth’s biodiversity is. All of the estimates obtained so far have a large prediction range, hundreds of thousands or even millions of species from the smallest estimates to the largest ones. On top of this shaming ignorance, our planet’s biodiversity is highly threatened. Solid evidence indicates that we are facing a massive extinction event, driven unfortunately by our own activities. The most recent evidence indicates that a large portion of extent species, approximately a third of them, is facing a high risk of extinction (See www. iucnredlist.org). Technically a high risk of extinction means that if all variables affecting the demography and ecology of those species continue as they are now, they are going to disappear in 100 years or less. Therefore, it is crucial to estimate more accurately how many species live on our planet; otherwise it is going to be impossible to develop efficient strategies for protecting this diversity.

On a recent publication, Camilo Mora and collaborators estimated how many species are on Earth, using a novel approach based on the predictable pattern of diversity observed in the hierarchical taxonomic classification system. Their results indicate that there are approximately 8.7 million (± 1.3 million) of eukaryote species. If we considered that 1.2 million species have been catalogued, more than 85% of existing species on Earth have not been scientifically described.

I encourage you to read the whole paper and know more about this fundamental question in science:

Mora C, Tittensor DP, Adl S, Simpson AGB, Worm B (2011) How Many Species Are There on Earth and in the Ocean? PLoS Biol 9(8): e1001127. doi:10.1371/journal.pbio.1001127